Fig. 1. (a)–(g) Fabrication procedure of ZEONEX based rectangular polymer optical fiber preform and (h) image of the rectangular preform after a segment of it was drawn into rectangular optical fiber.

Fig. 2. (a) Cross section of the ZEONEX rectangular optical fiber with light guidance through the core and (b) simulated profile of the core mode.

Fig. 3. 3D surface profile measurement result of the ZEONEX rectangular optical fiber.

Fig. 4. Schematic illustrations of (a) axial (side view) and (b) radial (cross sectional view) aspects of the focused laser beam onto a circular fiber without IM oil. The red region in (a) indicates the elongated focal region. Microscope images of fs laser inscribed regions in circular fiber in (c) the absence and (d) presence of IM oil.

Fig. 5. Schematic illustrations of (a) axial (side view) and (b) radial (cross sectional view) parts of focused laser beam onto the rectangular fiber without IM oil.

Fig. 6. Microscope images of FBGs inscribed in ZEONEX rectangular fiber (a) without and (b) with IM oil. Reflection spectra of the inscribed FBGs (c) with IM oil in circular fiber, (d) without and (e) with IM oil in rectangular fiber. (f) Cross sectional view of the grating in (a), where the red dashed circle refers to the core and the black line refers to the laser irradiated region. (g) Schematic illustration of the focused laser beam in Gaussian form, and the red arrow shows the beam direction.

Fig. 7. Reflection spectrum of the FBG inscribed in ZEONEX rectangular fiber using 248-nm UV laser and phase mask technique.

Fig. 8. Reflection spectrum of the FBG inscribed in ZEONEX rectangular fiber using fs laser exhibiting peaks at 866.8, 1013, and 1511.3 nm.

Fig. 9. Experimental setup for strain measurement. Inset shows the FBG under investigation and the glued localities of the fiber. ZRF, ZEONEX based rectangular fiber; BBS, broadband source.

Fig. 10. (a) Spectral shift of the FBG peak (1511.3 nm) with applied strain. (b) Wavelength shift of the FBG peak with increasing and decreasing strain for three cycles of measurement with 1% change in strain for each cycle.

Fig. 11. (a) Spectral shift of the FBG peak (866.8 nm) with applied strain. (b) Wavelength shift of the FBG peak with increasing and decreasing strain for three cycles of measurement with 1% change in strain for each cycle.

Fig. 12. Wavelength shift of the FBG corresponding to peaks at (a) 1511.3 nm and (b) 866.8 nm with increasing temperature.